In a trial involving 80 patients with irritable bowel syndrome (IBS), investigators from Harvard Medical School’s Osher Research Center and Beth Israel Deaconess Medical Center in Boston found that the so-called "placebo effect" may be more than just thinking that you’re taking a real drug.

Placebo Patients Experience Greater Symptom Relief

Ted Kaptchuk, ODM, an associate professor of medicine at Harvard Medical School and director of the Asian Medicine and Healing Program, and colleagues randomly assigned patients to one of two groups: those who were informed that they were to take placebo pills twice a day and those who received no treatment, but had the same quality of interactions with health care providers. In fact, the placebo pills were given out in a bottle labeled “placebo” and described as “placebo pills made of an inert substance, like sugar pills, that have been shown in clinical studies to produce significant improvement in IBS symptoms through mind-body self-healing processes.”

After three weeks of treatment, nearly twice as many patients taking a placebo reported improvements in their symptoms as those who received no treatment, 59% vs. 35%. Moreover, patients taking a placebo doubled their rate to improvement, meaning they felt better more quickly, at almost the same rate if they had taken actual medications for their IBS. Midway through the study, side effects were reported by three placebo patients. By the end of the study, five placebo patients reported side effects, such as respiratory infection, pain, runny stools, and rash.

Kaptchuk and his team questioned the ethics of prescribing a placebo without a patient’s knowledge and designed their study to determine whether the placebo effect would occur when a patient is informed that they are taking a placebo. Why a placebo might help reduce symptoms isn’t entirely clear.

“We told the patients that they didn’t have to even believe in the placebo effect. Just take the pills,” Kaptchuk says in a prepared statement. “Nevertheless, these findings suggest that rather than mere positive thinking, there may be significant benefit to the very performance of medical ritual. I’m excited about studying this further. Placebo may work even if patients know it is a placebo.”

The study is published in PLoS ONE and was funded by the National Center for Complementary and Alternative Medicine and Osher Research Center at Harvard Medical School.